oo-

¹

1. a combining form meaning “egg,” used in the formation of compound words:

   oogamous.

o'o

²

or 'ō·'ō

[ oh-oh ]

noun

, plural o’·os.

1. any of several species of Hawaiian birds of the extinct genus Moho, especially the extinct M. nobilis ( Hawaiian o'o ), which had black plumage and two tufts of yellow plumes used to make ceremonial robes for the Hawaiian kings. The last surviving species was M. braccatus ( Kauai o'o ), classified as extinct in 1987.

oo-

combining_form

1. egg or ovum

   oosperm

Word History and Origins

Origin of oo-¹

< Greek ōio-, combining form of ōión egg ¹

Origin of oo-²

First recorded in 1885–90; from Hawaiian ʿōʿō

Word History and Origins

Origin of oo-¹

from Greek ōion egg ¹

Example Sentences

His personal assistant, U Myint Oo, confirmed his death, in a hospital.

From New York Times

He said that Mr. Tin Oo had a weak heart and died of kidney failure and pulmonary edema.

From New York Times

Once one of the most powerful figures in what is now Myanmar, Mr. Tin Oo founded the National League for Democracy, the country’s main opposition party, with Daw Aung San Suu Kyi during a violent failed pro-democracy uprising in 1988.

From New York Times

She is again in detention, and it was not clear whether she had been informed of Mr. Tin Oo’s death.

From New York Times

“Daw Aung San Suu Kyi would be deeply saddened to hear of his passing, as she has lost a trusted confidant,” Mr. Myint Oo said.

From New York Times

Words That Use Oo-

What does oo- mean?

Oo- is a combining form used like a prefix meaning “egg.” It is used in many scientific terms, especially in biology.

Oo- comes from the Greek ōión, meaning “egg.” The Greek ōión helps form the word ōophóros, meaning “egg-bearing” and is the source of the combining form oophoro-, used to indicate the ovary.

Distantly related to the Greek ōión is the Latin word for egg, ōvum, source of the related combining forms ov-, ovi-, and ovo-, also used to mean “egg.” The Latin ōvum is ultimately the origin of ovario-, used, like oophoro-, to mean “ovary.”

What are variants of oo-?

When combined with words or word elements that begin with a vowel, oo- becomes o-, as in oidium.

Examples of oo-

One example of a scientific term that features the combining form oo- is oocyte, “an immature egg cell of the animal ovary,” including in humans.

The oo- part of the word means “egg,” as we have seen. The second part of the word is -cyte, from the Greek kýtos, means “cell.” Oocyte literally translates to “egg cell.”

What are some words that use the combining form oo-?

• ooblast
• oogamy
• oogenesis
• oolite (using the equivalent form of oo- in New Latin)
• oology
• oophyte

What are some other forms that oo- may be commonly confused with?

• ob-
• oc-
• opto-
• onco-

Not every word that begins with the exact letters oo- is necessarily using the combining form oo- to denote “egg.” Oodles, ooh, and ooze are three examples. Learn what oodles, ooh, and ooze mean and where they come from at our entries for the words.

Break it down!

The combining form -logy is used to name sciences or bodies of knowledge. What does oology, a branch of ornithology (science of birds), study?